1. Field of the Invention
This invention relates in general to the construction of turbo-compressors and, in particular, to a new and useful multi-stage axial flow compressor which is provided with individual stages which include a runner combination and a guide wheel.
2. Description of the Prior Art
The invention provides a multistage axial flow compressor having a degree of reaction or percentage reaction of approximately 100%. Each compressor stage comprises a tandem cascade formed by two consecutively arranged rotor blade rings and a single guide blade ring. A so-called tandem cascade is a compressor stage which comprises two consecutively arranged rings of rotor blades or a rotor wheel which carries two consecutively arranged blade rings and a guide blade ring adjacent these rings.
By the inventive arrangement of the stages between the initial stage and the final stage with each stage including a moving ring with two rows of moving baldes in a single guide blade row there is a vast improvement over the construction of the prior art wherein a single row of rotor blades and a single row of guide blades are employed inasmuch as the guide blade ring is saved in each stage while obtaining the same circumferential effect. With such a construction it is therefore possible to reduce the entire blading by approximately 45% and the bladed overall length by approximately 30% so that the length of the rotor shaft can also be correspondingly shortened.
Another advantage of the present construction in contrast to the prior art is that the inlet and outlet wheels may be omitted so that the blading expenditures may be further reduced and the overall length may be shortened in addition. A substantial advantage is obtained with compressors having stages of this construction because they are less sensitive to changes of the outflow angle. This leads to a substantially more favorable behavior in the part load duty range so that due to a relatively flat characteristic curve of operation, a considerably wider characteristic field is available.
A further advantage of the invention has been found by testing such an arrangement employing two rotor blade rows and a guide blade row where it has been shown that an extraordinarily favorable effect on the secondary and tip clearance losses is obtained so that a basic improvement of the internal efficiency of the compressor can be obtained. With such a construction in a single stage axial blower the location of the surge limit can be favorably influenced.
By constructing the stages between the initial and final stage so that it comprises a plurality of stages each including a moving ring with two rows of moving blades and a single guide blade row in a compressor having a percentage reaction of about 100%, a considerable load reserve is present in the guide blade rows. Thus with the compressors having a percentage reaction of 100% almost the entire deflecting work is made by the rotor blade rows so that the guide blade rows are relieved to an extraordinary degree. This condition however applies only to axial flow compressors having a percentage reaction of substantially 100%.
Accordingly it is an object of the invention to provide a multistage axial flow turbine and blast furnace compressor blower which comprises a compressor having a reaction of 100% and with a rotatable shaft having a plurality of rings with blades defining moving blade rows interspersed with a plurality of guide blade rows and wherein the rows are arranged in a plurality of intermediate stages between an initial stage and a final stage and with the intermediate stages each including a moving ring with two rows of moving blades and a single guide blade row and the initial stage comprising at least one of the following: a single moving blade row or a single guide blade row in a moving ring with two rows of blades and the final stage comprising either: a single guide blade row and a single moving blade row or a single guide blade row, and wherein the shaft is foreshortened by providing one row of the guide blades to take up the pressure of two rows of the moving blades in the intermediate stages at 100% reaction between said initial and said final stages.
A further object of the invention is to provide a multi-stage axial flow compressor which is simple in design, rugged in construction and economical to manufacture.
For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawing.